Installations for reprocessing irradiated nuclear fuels have large so-called hot cells wherein the process components are accommodated. These cells are shielded with respect to radiation and contain frames known as racks in which the processing components are mounted.
Maintenance work inside the large radioactive cells has to be performed without personnel entering the cell. Maintenance work is therefore carried out by travelling remote handling apparatus. In this connection, the racks holding the processing components are placed along the walls of the hot cell in a modular configuration to facilitate remote handling. This makes it possible to exchange a complete rack or parts of a rack.
Within the racks, the conduit system for supplying the processing components is almost completely welded. Only a few components which are subject to wear are equipped with detachable conduit connections. The conduit connections between racks and those conduit connections leading to a curtain of conduits at the wall of the cell or to conduits extending through the wall must also be fitted with detachable conduit connections.
When a rack is exchanged, all the conduits which connect two racks directly with one another or which connect a rack to conduits leading through the wall of the cell have to be separated by remote handling and reconnected when a new rack has been installed. It is necessary for whole sections of the conduits to be removed in order to enable the rack to be dismantled, since the conduits would prevent the exchange, that is, the removal of the rack.
Removable conduit connecting units or interconnecting conduit sections known as jumpers are therefore used which have connectable flanges at the respective ends thereof. When a conduit leading through the wall of the cell is connected to a conduit extension in the rack, an interconnecting conduit section is inserted between the stationary end flange of a conduit extension welded to a plate mounted on the wall of the cell and a conduit extension of an apparatus arranged in the rack. The removable conduit sections are then coupled to these two end flanges.
The conduits of the processing components arranged in the rack terminate in conduit extensions mounted on a conduit connecting plate on the rack.
Between the two stationary end flanges of the conduit connecting plates which have to be connected, there is a predetermined space into which the interchangeable or removable interconnecting conduit section is inserted or from which it is removed. The conduit flanges and end flanges are joined together by clamping ring couplings or threaded fastener connections.
The removal or insertion of the conduit section has to be carried out by remote handling. This is not simple, since the operator carrying out the joining process can only watch the process by observing a television monitor and operate accordingly. Attempts to insert the removable conduit section are often unsuccessful.